Tractor has a different job than a car. If you rarely use it, just burn diesel, don't risk your injector pump with seed oil which is not what it's made for.
If you use it a lot, nothing is cheaper than electric, that's just how it is.
If you're growing your own rape seed, you've got 1% efficiency on the photosynthesis, maybe 50% of the plant's energy goes to oil, then the engine is 40% efficient.
Compare with 20% efficient solar panels, 80% efficient battery and 95% efficient motor. It just doesn't compare...
The only place where electric is really impossible is if you've got a thousand horse tractor pulling a drill all day and blowing 50 gallons of diesel per day. And if you're that guy, it's really hard to avoid burning diesel.
